1. From consideration of the ionic radii, what number of nearest neighbors do you expect around the + ion in the following ionic compounds? Beryllium oxide, rubidium fluoride (careful with this one), magnesium oxide, iron (2+) oxide, silicon dioxide (quartz). How many silicon atoms do you expect to neighbor each oxygen in SiO2?

2. (a) Calculate the value of critical radius ratio for coordination number of 4 in an ionic compound (that is, convince yourself by calculation that the value given in the text is correct.) (b) repeat for a coordination number of 8.

3. Sketch a face centered cubic unit cell. Outline two non-parallel close-packed planes of atoms. How many atoms are in the cell?

4. Platinum crystallizes with a face centered cubic lattice. The atomic radius of platinum is 0.138nm, and the atomic mass is 195.1 . (a) Calculate the lattice parameter of Pt from these data. (b) Calculate the density of Pt in g/cm3 from these data (take care with the units). Compare your calculated value with the measured density of Pt as tabulated in the text.

5. Assuming that the atoms are hard spheres in contact, calculate the theoretical value for c/a in the hexagonal close packed crystal structure of a metal. (Hint - see the text for the unit cell. There are regular tetrahedra of atoms in the unit cell, and you calculated the height of these in Homework 1).

6. Estimate how many electrons you contain (you should be able to come up with an estimate within about 15% of the true value without too much effort)